On the subject of SR, it would be useful if people read what the man himself actually wrote (examples are, yet again, quoted below), then you would all stop chasing this red herring.
In respect of the theory of relativity, again it would be useful if people read what the man himself actually wrote, then you would realise that there is no observational light for an observer to observe with. Just deploying the words observer, frame of reference, and light, does not make it so. The light which Einstein refers to is a conceptual constant used to calibrate duration and distance. In sum: he has shifted the actual timing differential which occurs between time of existence and time of receipt of photon based representation of that, to the other end of the physical process, ie it is deemed to be a characteristic of physical existence.
SR definition
Einstein 1916 section7
"At this juncture the theory of relativity entered the arena. As a result of an analysis of the physical conceptions of time and space, it became evident that in reality there is not the least incompatibility between the principle of relativity and the law of propagation of light, and that by systematically holding fast to both these laws a logically rigid theory could be arrived at. This theory has been called the special theory of relativity to distinguish it from the extended theory, with which we shall deal later."
Einstein 1916 section 18
"provided that they are in a state of uniform rectilinear and non-rotary motion...The validity of the principle of relativity was assumed only for these reference-bodies, but not for others (e.g. those possessing motion of a different kind). In this sense we speak of the special principle of relativity, or special theory of relativity."
Einstein 1916 section 22
"A curvature of rays of light can only take place when the velocity of propagation of light varies with position. Now we might think that as a consequence of this, the special theory of relativity and with it the whole theory of relativity would be laid in the dust. But in reality this is not the case. We can only conclude that the special theory of relativity cannot claim an unlimited domain of validity; its results hold only so long as we are able to disregard the influences of gravitational fields on the phenomena (e.g. of light)."
Einstein 1916 section 28
"The special theory of relativity has reference to Galileian domains, ie to those in which no gravitational field exists. In this connection a Galileian reference-body serves as body of reference, ie a rigid body...In gravitational fields there are no such things as rigid bodies with Euclidean properties; thus the fictitious rigid body of reference is of no avail in the general theory of relativity."
Einstein 1921 para 11:
"The development of the special theory of relativity consists of two main steps, namely, the adaptation of the space-time "metrics" to Maxwell's electro-dynamics, and an adaptation of the rest of physics to that altered space-time "metrics."
So, special relativity, as defined by Einstein, involves:
-only motion that is uniform rectilinear and non-rotary
-only fixed shape bodies at rest
-only light which travels in straight lines at a constant speed
It is not what was written in 1905. It is special because there is no gravitational force, or more precisely, no differential in the gravitational forces incurred.